• enPR: fĭn, IPA: /fɪn/

From Middle English fin, from Old English finn, from Proto-Germanic *finnō, *finǭ ("dorsal fin") (compare Dutch vin, German Finne, Swedish finne, fena), from Proto-Indo-European *(s)pīn- (compare Old Irish ind (“end, point”), Latin pinna (“feather, wing, fin”), Tocharian A spin (“hook”), Sanskrit स्फ्य (sphyá, “splinter, staff”).

fin (plural fins)

1. (ichthyology) One of the appendages of a fish, used to propel itself and to manoeuvre/maneuver.

   The fish's fins minimize water flow.

   • 1913, Joseph C[rosby] Lincoln, chapter IV, in Mr. Pratt’s Patients, New York, N.Y., London: D[aniel] Appleton and Company, →OCLC ↗:

     Then he commenced to talk, really talk. and inside of two flaps of a herring's fin he had me mesmerized, like Eben Holt's boy at the town hall show. He talked about the ills of humanity, and the glories of health and Nature and service and land knows what all.

2. A similar appendage of a cetacean or other marine animal.

   a dolphin's fin

3. A thin, rigid component of an aircraft, extending from the fuselage and used to stabilise and steer the aircraft.

   The fin stabilises the plane in flight.

4. A similar structure protruding from a projectile, used to help keep it on course.
5. (surfing) A similar structure on the bottom of a surfboard, used to help steer it.
6. A hairstyle, resembling the fin of a fish, in which the hair is combed and set into a vertical ridge along the top of the head from about the crown to the forehead.
7. A device worn by divers and swimmers on their feet.

   The divers wore fins to swim faster.

8. An extending part on a surface of a radiator, engine, heatsink, etc., used to facilitate cooling.
9. A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder.
10. (nautical) The conning tower of a submarine.

• (appendange of a fish)
• (appendage of a cetacean or other marine animal) flipper (of mammals)
• (aircraft component)
• (of a bomb) vane
• (hairstyle) Mohican
• (device worn by divers) flipper

• French: nageoire, (shark) aileron
• German: Flosse
• Italian: pinna
• Portuguese: nadadeira, barbatana
• Russian: плавни́к
• Spanish: aleta

• French: nageoire
• German: Flosse
• Italian: pinna
• Portuguese: nadadeira
• Russian: ласт
• Spanish: aleta

• French: empennage
• Italian: impennaggio
• Portuguese: estabilizador, aleta
• Russian: стабилиза́тор

• French: empennage
• Italian: impennaggio
• Portuguese: aleta
• Russian: стабилиза́тор

• French: palme
• Italian: pinna
• Portuguese: pé de pato, barbatana
• Russian: (seldom used in singular) ласт
• Spanish: aleta

fin (fins, present participle finning; simple past and past participle finned)

1. (transitive) To cut the fins from a fish, shark, etc.
2. (intransitive) (Of a fish) to swim with the dorsal fin above the surface of the water.
3. (intransitive) To swim in the manner of a fish.

   A neutrally buoyant diver does not need to fin to maintain depth.

4. (transitive) To provide (a motor vehicle etc) with fins.

From Yiddish פֿינף.

fin (plural fins)

1. (UK, formerly Australia, slang) a five-pound (£5) note; the sum of five pounds.

   Synonyms: fiver

2. (US, slang, dated) a five-dollar bill; the sum of five dollars.

   Synonyms: fiver, Lincoln

From French fin (“end”).

fin (plural fins)

1. (archaic, cinema, television) "The end".

   Synonyms: finis

2. (obsolete, road signs) Denotes the end of the road.

1. commune in the Somme department in France

fin (plural fins)

1. (telecommunications, US) Initialism of facility ID number
2. (police, UK) Initialism of force identification number